Research Of Paleozoic Tectonic Process In Northeast Xinjiang

Xinjiang Uygur Autonomous Region locates in the hinterland of Asia, which is one of the important part of the Central Asia continental orogenic zone in China. It is the best field laboratory of researching and explorating of new theories of the continental geology and dynamics. Researching Paleozoic tectonic process in North Xinjiang is not only the key to study structural evolution of the Central Asia continental orogenic zone, but also likely to offer an universal and particular example to study the global continental geology and dynamics.Physiognomy of complex geological frame and structure nowadays in North Xinjiang was caused by suffering superposition and alteration of the tectonic process which were the tectonization that was typical of the plate convergence and collision during the main stage of the orogenesis in Paleozoic and the intense tectonic process within the plate in Mesozoic and Cenozoic. However, relating to investigate the modes, courses and characteristics of the orogenetic process in Paleozoic and after orogenetic process, the cognitive divergence have still occurred. So, the Kelamaili ophiolitic melange, Bogeda Mountain, Bayingou ophiolitic melange, Saridala ductile shear zone and Yushugou terrane of high-pressure granulite facies in Kumishi area, Southern Tianshan are selected for subjects and many ways, for example, macroscopic and microscopic methods, qualitative and quantitative analysis are applied to this systemic research on magmatism, response of deposition, metamorphism, tectonic deformation and so on that are closely related to tectonic process and discuss furthermore the modes, characteristics and evolution of the tectonic process in Late Paleozoic in Northeast Xinjiang by means of lithology, tectonics and geochemistry.According to what is researched above, it is confirmed that, ① the protolith of Yushugou terrane of high-pressure granulite facies in south Tianshan is a basic ophiolite suite which was underwent complicated process of metamorphosing. To begin with, the suite had subducted lower crust and gone through metamorphism of high-pressure granulite facies, later due to the tectonic uplifting that had made the terrane get into the environment of deep crust, the terrane suffered metamorphism of mid-pressure granulite facies, subsequently it had underwent fast tectonic uplift and occurred metamorphism of amphibolite facies. It is indicated that the plate of southTianshan oceanic crust underwent subduction, metamorphism and uplifting in succession through studying of the metamorphism process of the suite, and for the first time, the PTt track of the metamorphism process is ascertained in this research;?Oceanic basin-subducting and terrane-accreting occurred in late Ordocician at the northern margin of the Middle Tianshan Belt where was an arc active belt.In Late Middle-Carboniferous, the small Middle Tianshan oceanic basin was closed, what came next was slant abutment between Zhungar plot and Yili-Middle Tianshan plot and later occurred brittle-ductile ductile shearing with nearly level, high temperature, low speed and right lateral strike-slipping.?Based on the geochemical characteristics with close relations to active continental margin of sillcalite at Bayingou which is not one part of an ophiolite suite and MORB in Bayingou ophiolitic melange which its magma source was influenced by input of the subduction components and according to areal geological data, one new idea is brought forward for the first time that the Bayingou ophiolitic melange standing for Paleo-structural setting of oceanic basin is bank-arc basin that occurred spreading and gradually closed between Early Carboniferous and late middle carboniferous epoch;(4) Three different volcanic rock associations of N-MORfk T-MORB and OIB are decomposed in Kelamaili ophiolitic melange and it is implied that different plots occurred accreting during ocean basin-subducting, which approved that Kelamaili ophiolitic melange is a suture zone between Siberia Plate and Kazakhsta Plate;?Slump-deposition structure, extending molasse formation of and basite which is related to continental rift and pullapart zone or primary rift in continent, that it is suggested that there was an extensional setting after orogeny in early Permian in Northeast Xinjiang.Colligating many predecessors' results and this research, a mode of tectonic process evolution is constructed in Northeast Xinjiang and compartmentalized four stages as follows: € -O2 , oceanic basin-expanding stage;O3-S-D , oceanic basin-subducting, terrane-montage and accreting stage;D-C2 oceanic basin-closed in southern Tianshan and Bayingou and Tianshan-cohering fully stage;D3-C3, collision and orogenesis stage;Pi, extending after orogenesis stage.